Two-dimensionally electronically-steerable artificial impedance surface antenna

Abstract

A method and apparatus for electronically steering an antenna system is provided. A surface wave is propagated along each of a number of surface wave channels formed in each of a plurality of radiating elements to form a radiation pattern. Each surface wave channel in the number of surface wave channels formed in each radiating element in the plurality of radiating elements is coupled to a transmission line configured to carry a radio frequency signal using a surface wave feed in a plurality of surface wave feed associated with the plurality of radiating elements. A main lobe of the radiation pattern is electronically steered by controlling voltages applied to a plurality of switch elements connecting a plurality of impedance elements in each of the number of surface wave channels.

What is claimed is: 
     
       1. An apparatus comprising:
 a plurality of radiating elements, wherein each radiating element in the plurality of radiating elements comprises a number of surface wave channels in which each of the number of surface wave channels is configured to constrain a path of a surface wave and each radiating element in the plurality of radiating elements comprises:
 a plurality of switch elements, and 
 a plurality of impedance elements; and 
 
 a plurality of surface wave feeds, wherein a surface wave feed in the plurality of surface wave feeds is configured to couple a surface wave channel in the number of surface wave channels of a radiating element in the plurality of radiating elements to a transmission line configured to carry a radio frequency signal; and 
 wherein the plurality of radiating elements and the plurality of surface wave feeds form an artificial impedance surface antenna that is configured to be electronically steered in a theta direction and a phi direction. 
 
     
     
       2. The apparatus of  claim 1 , wherein the artificial impedance surface antenna operates at a frequency between about 26.5 gigahertz and about 40 gigahertz. 
     
     
       3. The apparatus of  claim 1 , wherein the artificial impedance surface antenna operates at a frequency of about 30 gigahertz with an aperture efficiency greater than about 25 percent. 
     
     
       4. The apparatus of  claim 1 , wherein the plurality of switch elements of each surface wave channel of the number of surface wave channels enables creating a surface impedance profile of high surface impedance and low surface impedance for the each surface wave channel. 
     
     
       5. The apparatus of  claim 4 , wherein the surface impedance profile is a square-wave-type modulation. 
     
     
       6. The apparatus of  claim 4 , wherein the high surface impedance and the low surface impedance are modulated to enable scanning in the theta direction and in the phi direction. 
     
     
       7. The apparatus of  claim 1 , wherein each switch element in the plurality of switch elements is a PIN diode that has an inductance state and a capacitance state. 
     
     
       8. The apparatus of  claim 1 , wherein each switch element in the plurality of switch elements is a Schottky diode that has only two states. 
     
     
       9. The apparatus of  claim 1 , wherein each switch element in the plurality of switch elements is a semiconductor switch that has only two states. 
     
     
       10. The apparatus of  claim 1 , wherein each switch element in the plurality of switch elements is a microelectromechanical systems switch diode that has only two states. 
     
     
       11. The apparatus of  claim 1 , wherein each switch element in the plurality of switch elements is a phase-change material switch that has only two states. 
     
     
       12. The apparatus of  claim 1 , wherein each switch element in the plurality of switch elements is a high frequency diode that has only two states. 
     
     
       13. The apparatus of  claim 1 , wherein an impedance element in the plurality of impedance elements is selected from one of a metallic strip, a patch of conductive paint, a metallic mesh material, a metallic film, a deposit of a metallic substrate, a resonant structure, a split-ring resonator, an electrically-coupled resonator, and a structure comprised of one or more metamaterials. 
     
     
       14. The apparatus of  claim 1 , wherein an impedance element in the plurality of impedance elements has a pattern formed by a series of a same shape. 
     
     
       15. The apparatus of  claim 14 , wherein the same shape is selected from one of a diamond-type shape and a hexagonal-type shape. 
     
     
       16. An artificial impedance surface antenna comprising:
 a plurality of radiating elements, wherein each of the plurality of radiating elements comprises a number of surface wave channels in which each of the number of surface wave channels is configured to constrain a path of a surface wave and wherein each of the plurality of radiating elements comprises:
 a plurality of impedance elements located on a surface of a dielectric substrate wherein an impedance element in the plurality of impedance elements has a pattern formed by a series of a same shape selected from one of a diamond-type shape and a hexagonal-type shape, and 
 a plurality of switch elements located on the surface of the dielectric substrate in which each of the plurality of switch elements has a first state and a second state; and 
 
 a plurality of surface wave feeds configured to couple the number of surface wave channels of each of the plurality of radiating elements to a number of transmission lines. 
 
     
     
       17. A method for electronically steering an antenna system, the method comprising:
 propagating a surface wave along each of a number of surface wave channels formed in each of a plurality of radiating elements to form a radiation pattern; 
 coupling each surface wave channel in the number of surface wave channels formed in each radiating element in the plurality of radiating elements to a transmission line configured to carry a radio frequency signal using a surface wave feed in a plurality of surface wave feeds associated with the plurality of radiating elements; and 
 electronically steering a main lobe of the radiation pattern in a theta direction and a phi direction by controlling voltages applied to a plurality of switch elements connecting a plurality of impedance elements in each of the number of radiating elements. 
 
     
     
       18. The method of  claim 17 , wherein electronically steering the main lobe comprises:
 applying a first level of voltage or a second level of voltage to each of the plurality of switch elements to create a surface impedance profile for each surface wave channel of the number of surface wave channels. 
 
     
     
       19. The method of  claim 17 , wherein electronically steering the main lobe comprises:
 applying a first level of voltage or a second level of voltage to each of the plurality of switch elements to modulate between high surface impedance and low surface impedance. 
 
     
     
       20. An apparatus comprising:
 a plurality of radiating elements, wherein each radiating element in the plurality of radiating elements comprises a number of surface wave channels in which each of the number of surface wave channels is configured to constrain a path of a surface wave and each radiating element in the plurality of radiating elements comprises:
 a plurality of switch elements, and 
 a plurality of impedance elements, wherein an impedance element in the plurality of impedance elements has a pattern formed by a series of a same shape selected from one of a diamond-type shape and a hexagonal-type shape; and 
 
 a plurality of surface wave feeds, wherein a surface wave feed in the plurality of surface wave feeds is configured to couple a surface wave channel in the number of surface wave channels of a radiating element in the plurality of radiating elements to a transmission line configured to carry a radio frequency signal.